The present invention relates to electronic musical performance through keyboard electronic instruments, e.g. synthesizers, electronic pianos, organs and controller keyboards, and more particularly to the performer access to and adjustment of touch response parameters that enhance the expressiveness of such instruments.
The performer's physical input to the keyboard results in a tactile and sonic feedback from the instrument that characterizes its expression. For example, the acoustic piano is generally regarded as a very expressive instrument due in part to the satisfying tactile response of a piano action and the way key velocity influences the sound quality of a note (e.g., loudness, timbre). Accordingly, touch response parameters fall into two categories: those that affect what the performer actually senses through his fingers as he plays a note (e.g., key imbalance, inertia), and those that control the dynamics of individual notes as they are played. (e.g., key velocity).
The piano action has undergone several hundred years of development and consists of nearly one hundred parts per key. Early electronic keyboards had very simple organ type actions consisting of a plastic key and spring that electronically produced a note when the depressed key closed a switch. Musicians trained on acoustic pianos complained that these keyboards lacked expression because the tactile response was "soft" and the sound produced was independent of key velocity.
Electronic keyboards have since incorporated various features to approximate the "piano key feel". For example, weighted wooden keys simulate the static imbalance in a piano action. This imbalance provides a relatively constant restoring force of several ounces and causes the key to track the finger action no matter how rapidly a note is played.
There have been corresponding improvements in the sensing of key dynamics. Velocity sensitive keyboards typically sense key velocity by multiple switch contacts, electrooptical, electrostatic or electromagnetic means. The sensed velocity is in turn used to electronically control the sound quality of the note produced.
Some prior art keyboards include what is known as aftertouch control wherein further depression of the key after it has reached its normally depressed position, alters the quality of the tone. So called pressure sensitive keyboards typically sense aftertouch by a piezoelectric element contacted by the key or compression of a variable resistance conductive strip. Such techniques are generally considered to enhance keyboard expressiveness although no direct analogy to a conventional piano action applies.
A disadvantage to most prior art keyboards that approximate a piano key feel is the simulation of piano key imbalance alone. Dynamic effects such as inertial forces that alter the tactile feedback significantly as a key is played faster, are not simulated. The hammer in a piano action travels approximately two inches for a 1/4 inch displacement of the key. This mechanical advantage causes the hammer inertia to dominate the total inertia sensed by the performer. At fast tempo this can require peak applied forces that are four or five times the static imbalance. Typically a state of the art weighed key action requires less than twice the imbalance force at similar tempo.
Since evaluation of tactile response is subjective, not all musicians applaud the simulation of piano effects. Some prefer an organ to piano touch because of the quickness of its light touch and ability to trill a note without added exertion. Still others judge tactile response in relationship to the musical piece performed; a controlled pianistic touch may be preferred for classical performance, and the speed of an organ action for more contemporary music.
Because the tactile response parameters are fixed by the physical properties of the key mechanism, the performer must settle for the manufacturer's notion of "optimum key feel" without any provision to tailor response to personal preference.
A further disadvantage is that prior art keyboards usually do not monitor the dynamic interaction of performer and key over the full extent of key travel. For example, velocity sensing often occurs only as the key nears the keybed and aftertouch control senses applied pressure after the key is fully depressed. The switch closure that initiates sound generation is also located near the end of travel. Continuous sensing of the performer's applied force and key velocity, and the ability to control note on/off at some interim key position are not generally implemented.
Consequently, the prior art while overcoming some deficiences of early electronic keyboards, has not fully realized the touch response capability or variability of key operated electronic instruments. This includes accurate simulation of a "piano key feel" and features that produce effects dissimilar to a conventional piano or organ that nonetheless improve the expressiveness of the instrument.